"As had been publicized, we had a wonderful get-together on Friday, a lengthy get-together," Tracy said. "I came home and spent quite a bit of time, many hours, talking and reflecting on a lot of things past and present. I really got to the point ... where I was strongly coming to the conclusion that I'm no longer the proper fit for this club."
Tracy, who previously managed the Dodgers and the Pirates, walked away from a guaranteed salary of $1.4 million in 2013.
The move was not forced. Geivett said he expected Tracy back for next season. "It was a surprise to me," Geivett said.
The team is expected to interview bench coach Tom Runnells, who managed the Montreal Expos in 1991 and '92, and Stu Cole, a longtime manager in the Rockies' farm system who most recently has served as the manager at Triple-A Colorado Springs. No candidates from outside the organization have emerged.
Geivett said by phone that the team would meet soon to discuss what it wants in the new manager.
"Right now, there has been a lot to digest, but there are characteristics that we would like in the new manager," Geivett said. "We will be working on a plan."
Poor starting pitching in the beginning of the season led to a year of upheaval in Tracy's final year with the Rockies.
When pitching coach Bob Apodaca resigned in June because of fatigue, the Rockies went to co-pitching coaches Bo McLaughlin and Jim Wright. Shortly thereafter, the team went to a four-man rotation, with three relievers also throwing on a starter-like schedule, and starters were limited to around 75 pitches.
The Rockies went back to a five-man rotation late in the year, but announced that next season there would still be a pitch count -- higher than 75 but not like most clubs, which often let pitchers go to 120 -- and the hybrid relievers would exist in some form.
The Rockies said the radically different pitching plan was not just a reaction to the poor season. The club tracked pitching over 20 seasons and saw high injury rates and dramatic drops in effectiveness when starters log large numbers of innings.
However, the pitch counts this past season often limited Tracy's ability to match up with the opponent's bench and bullpen. Tracy enjoys that type of managing.
Also, general manager Dan O'Dowd relinquished day-to-day Major League duties to Geivett, who was moved to an office inside the Rockies' clubhouse and was added to the traveling party for all road trips. Tracy worked directly with Geivett, who also spent time learning all parts of the Major League operation.
Tracy and Geivett spent Friday discussing all parts of the operation, from how the game would be run to the coaching staff before reaching his decision.
Tracy did not discuss any specifics that led to his decision, but said he was uncomfortable with the amount of change.
"There have been a number of things that I really feel when I was asked to be the manager of the club, and the different conditions that were laid out before me, and where things are now, there are quite a few things that are much, much different," Tracy said. "But I want to add this: the tough part is so many uniformed and non-uniformed personnel, my coaches and especially my players, I have developed a love affair with [them]. I hold the utmost respect for each and every one of them."
Tracy said he wants to manage or be on the field in the future, but said his decision with the Rockies had nothing to do with other opportunities that may exist.
Geivett said the strategies discussed with Tracy will be hammered out in discussions with the new manager.
"I think those are all great discussions for when we talk," Geivett said. "We, as a franchise after 20 years of play here, have learned a lot about our home park and we need to make that to our advantage."
But part of the issue in 2012 was injuries. Shortstop Troy Tulowitzki, first baseman Todd Helton, outfielder-first baseman Michael Cuddyer and outfielder Eric Young Jr. suffered season-ending injuries, and pitchers Jhoulys Chacin and Jorge De La Rosa missed much of the year with injuries.
"Once healthy, we're in good shape," Geivett said. "I feel we don't get enough credit for the talent that we have here, when healthy. But at the same time, you've got to win games."
The Rockies will seek their sixth manager as they prepare for their 21st season. Tracy was preceded by Don Baylor (1995-98), Jim Leyland (1999), Buddy Bell (2000-April 26, 2002) and Hurdle (April 26, 2002-May 29, 2009).
Players were trying to get their minds around the surprise decision on Sunday.
Carlos Gonzalez, the Rockies' lone All-Star Game representative in 2012, received his chance to play regularly in the Majors in 2009, when Tracy stuck with him through an early slump.
"Jim Tracy's resignation is something I truly regret, since he gave me the chance to play in the Major Leagues and prove my talent," Gonzalez said in a statement. "It has always been an honor to play for him. I always believed he would have a chance to be with us next year.
"He is truly respected inside our clubhouse and I hoped he would be with us so he could help us improve and have a better season in 2013. Sadly, we had one of the worst seasons in franchise history and when these things happen, our jobs are at stake."
Veteran left-hander Jeff Francis, who was with the Rockies when Tracy arrived as bench coach and returned to the team this season, is eligible for free agency, but he has stated that he wants to return.
"I was surprised -- I guess it's an indication that maybe [there was] some frustration, I don't know," Francis said. "I was expecting him to be back, too."
Francis said he isn't sure how the managerial decision will play into his decision.
"There are a lot of factors, not only on my end but their end, too," Francis said. "I guess I'll just have to wait and see what my options are. It certainly wouldn't be a deal-breaker."
Some took to Twitter to express gratitude.
Tracy stuck with center fielder Dexter Fowler through horrendous slumps the past two years, and Fowler responded this year with career-best numbers in batting average (.300), on-base percentage (.389) and home runs (13).
Fowler tweeted, "Man I'm gonna miss Tracy, thanks for believing in me! You are a wonderful and stand up guy!"
Rookie infielder-catcher Jordan Pacheco, who finished fifth in the NL with a .309 batting average, which led NL rookies, tweeted, "Thank you skip for giving me an opportunity ... It was an honor to play for you."